The present invention relates generally to a method of and apparatus for locking an electrical plug to a power distribution panel having a sequential coupling guard and precluding removal of an electrical plug from such power distribution panel.
Power distribution panels employing sequential coupling guards are known in the art. An example is disclosed in U.S. Pat. No. 4,955,821 (hereinafter the ""821 patent) entitled xe2x80x9cMethod For Controlling Connector Insertion Or Extraction Sequence On Power Distribution Panelxe2x80x9d to the present inventor and assigned to a common assignee which is hereby incorporated by reference in its entirety into this specification.
FIGS. 1-5 are taken from the ""821 patent and represent the prior art. With reference to FIG. 1, there is shown a cam ring mechanism including a plurality of cam rings 11-15 mounted in an upper and lower channel member 20 and arranged along a common axis 30 best seen in FIG. 2 which passes through the three and nine o""clock positions of each of the rings. The cam rings 11-15 are positioned at the rear of an array of electrical receptacles 21-25: the receptacle 21 may be a ground receptacle, the receptacle 22 may be a neutral receptacle, and the receptacles 23-25 may be for three-phase power. The receptacles are the type in which a plug must be twisted or rotated approximately 45xc2x0 before making a final electrical connection thereto.
Each cam ring 11-15 includes an outer cam surface 16 which is generally convex in shape. The cam surface 16 does not extend completely around the cam ring and is subtended by a clearance notch 17 and a locking notch 18. The clearance notch 17 and the locking notch 18 are generally concave in shape and are dimensioned to mate with the convex cam surface 16 on an adjacent cam ring. The clearance notch 17 is located between the one and two o""clock position on each cam ring and the locking notch 18 is located at the nine o""clock position. Each cam ring includes a pair of tabs 19 which extend toward the center portion of the ring and provide engagement means for turning the cam ring as more fully described below. Rotation of each cam ring is limited by stops 27.
In FIG. 1, each of the rings 11-15 is in an original, unrotated position. In FIG. 2, the first three rings 11-13 have been rotated clockwise as if an electrical connection has been made to the first three receptacles 21-23. The plugs inserted in the receptacles are not shown.
FIG. 3 shows an alternate embodiment of the invention in which each of the receptacles 22-25 is positioned behind an aperture 28 in a front panel 29 and access to the apertures 28 is controlled by a cover plate 32-35, respectively. Each of the cover plates 32-35 is mechanically coupled to the cam ring adjacent and to the left of the receptacles 22-25; that is, cover 32 is coupled to the cam ring 11, cover 33 is connected to the cam ring 12, cover 34 is connected to the cam ring 13, and cover 35 is connected to the cam ring 14. The connection between the cam rings and the various covers 32-35 is made by a link 37 best seen in FIGS. 4 and 5. It will be noted that there is no cover plate over the first receptacle 21. This is problematic as will be described below.
FIG. 4 shows a side view of the receptacle assembly 21 which comprises a conductive pin 41 and an insulating sleeve 42 which is spaced therefrom. The cover plate 32 which in one position blocks access to the adjacent receptacle 22 is shown rotated to an open position and is connected to the cam ring 11 by the link 37. The conductive pin 41 and the sleeve 42 are mounted on a support 43 and a coupling tab 44 extends from the rear of the pin 41 for connection to a cable or other conductive element as well known in the art.
A plug 46 comprises an electrical socket 47 and an insulating sheath 48 which are dimensioned to mate with the receptacle 21. The conductive socket 47 is coupled to a cable connector 50 which may be terminated to an electrical cable as well as known in the art. The forward portion of the insulating sheath 48 includes a pair of slots 49 which are dimensioned to receive the radially extending tabs 19 on the cam ring. The forward portion of the socket 47 includes two L-shaped slots 51 best seen in FIG. 5 which receive two oppositely directed locking pegs 52 on the rear portion of the pin 41. When the socket 47 is fully engaged with the pin 41, the locking pegs 52 are at the bottom of the respective L slots 51; and the socket 47 may be rotated clockwise to position each of the locking pegs 52 in the foot 53 of the respective slot 51 to lock the socket onto the pin 41. Rotation of the socket also rotates the cam ring through the engagement of the tabs 19 in the slots 49. The rotation of the cam ring is limited by the abutment of the tabs 19 against the stops 27.
Mode Of Operation
The coupling guard controls the sequence of connecting a plurality of plugs to a plurality of receptacles as explained below.
Referring first to FIG. 1, the cam ring 11 which surrounds the ground receptacle 21, may turn either clockwise or counterclockwise since the cam surface 16 is free to turn relative to the locking notch 18 on the cam ring 12. The cam ring 12 is not free to turn, however, since the locking notch 18 is in an abutting relationship with the cam surface 16 of the cam ring 11. In a similar way, the locking notch 18 of each of the cam rings 13-15 is in abutting relationship with the cam surface 16 of the cam ring to the immediate left. Rotating the cam ring 11 clockwise approximately 45xc2x0 will abut the tabs 19 against the stops 27 and will position the clearance notch 17 of the cam ring 11 adjacent the cam ring 12. in this position, the cam ring 12 is free to rotate since the cam surface 16 of the ring 12 will pass through the clearance notch 17 of the cam ring 11. After the cam ring 12 has been rotated clockwise approximately 45xc2x0, the clearance notch 17 of cam ring 12 will be adjacent the cam ring 13. This will allow the cam ring 13 to be rotated; and in a similar fashion, the cam rings 14 and 15 may likewise be rotated once the cam ring immediately adjacent and to the left has been rotated clockwise to position the clearance notch 17 adjacent the cam ring which is next to be rotated.
In the manner described above, a series of plugs which must be rotated to couple with a series of receptacles can only be connected to the receptacles 21-25 in sequence from left to right. Engagement means on the cam rings such as the tabs 19 may be used to interlock with a plug which is inserted into the receptacle and to turn in response to a rotation of the plug. The clockwise rotation of the plug and the cam ring allows the adjacent cam ring to the right to be turned and thus the sequence of connections to be made. Plug and receptacle connectors such as shown in FIGS. 4 and 5 which require a partial turn or twist in order to make final electrical connection to a receptacle are well known in the art. Such connectors can be used with the apparatus of FIG. 1 with the result that the several plugs will have to be coupled to the plural receptacles in the predetermined sequence.
The apparatus of FIG. 1 will also insure that the disconnection of the several plugs is made in the correct sequence. As shown in FIG. 2, once the cam rings 12 and 13 have been rotated 45xc2x0 clockwise, the cam surface 16 of the cam rings 12 and 13 engages the clearance notch 17 of the cam rings 11 and 12, respectively. As a result, the cam rings 11 and 12 are locked against rotation; and cam ring 13 must be rotated counterclockwise to align the locking notch 18 of the cam ring 13 with the cam ring 12. Once this alignment has been made, it will be possible to rotate the cam ring 12 counterclockwise to align the locking notch of the ring 12 with the cam ring 11. Thus, the rings as shown in FIG. 2 may be rotated 45xc2x0 clockwise one at a time starting with the ring 13 in order to disengage the peg and L-slot lock and release the plugs from the receptacles 23, 22, and 21. If plugs have been connected to all five receptacles, the plugs coupled to the three power receptacles 23, 24, and 25 must be disconnected before the plug coupled to the neutral receptacle 22 or the plug coupled to the ground receptacle 21 can be disconnected.
In a further embodiment of the invention, the cover plates as shown in FIGS. 3 and 4 are used to block access to the receptacles in order to further insure that the connections are made to the receptacles in the proper sequence. As shown in FIG. 3, the receptacles 23-25 are located behind apertures 28 in the front panel 29 which may be blocked by the cover plates 33-35. The cover plates are attached by a link 37 to the cam ring immediately to the left of the receptacle over which the cover plate is located. The cover plate 32 for receptacle 22 has been rotated out of the way by rotating the cam ring 11 clockwise. As shown in conjunction with FIG. 4, slots 49 may be provided in the sheath 48 around the socket 47 to engage the tabs 19 and turn the cam ring 11. Once the receptacle 22 has been uncovered, as shown in FIG. 3, a plug may be inserted into the receptacle 22 and the plug turned clockwise to slide the cover plate 33 away from the receptacle 23. The complete connection to the five receptacles 21-25 may be made using the same sequence always rotating a cam ring to the left of a receptacle in order to slide the cover plate away from that receptacle. Once a connection has been made to any or all of the receptacles in a proper sequence, the reverse sequence must be used to disconnect the plugs as more fully explained above. Although panels having five receptacles have been shown in the various embodiments, the invention is equally applicable to panels having other numbers of receptacles. The invention is also applicable to installations in which the receptacles comprise socket connectors, and the plugs comprise pin connectors.
One problem associated with such panels is that any unblocked receptacles (unblocked by either a plug or a cover plate) are subject to misuse or vandalism. Specifically, since the power panel may be used in theater, carnival or amusement park locations where the general public may have access to the receptacles, there is a possibility that individuals will attempt to tamper with the receptacle openings. Unblocked receptacles present appealing targets to children or pranksters. Gum or debris may be inserted to block and hinder the insertion of plugs by malicious individuals or metal items might be inserted causing severe injury to the individual or damage to the equipment.
FIG. 6 depicts an improved version of the prior art power distribution panel including a lever 60 located exterior to the power distribution panel and operable with a first cover plate 62. As depicted in FIG. 6, the first cover plate 62 covers the first receptacle 21. The improvement overcomes the vulnerability of the first unblocked receptacle by using the additional cover plate 62 to cover the receptacle when no plug is inserted into the first receptacle 21. The cover plate 62 differs from the other cover plates 32-35 because the added cover plate 62 for receptacle 21 operates separately from operation of any of the receptacles 21-25. Because receptacle 21 is the first receptacle, there is no prior adjacent receptacle to rotate the cover plate 62.
In contrast to cover plates 32-35, the additional cover plate 62 is manually operated through the use of the lever 60 for opening and closing the cover plate 62 over the receptacle instead of relying on the rotation of the prior adjacent receptacle. A push button or other mechanism could be used to move the cover plate 62 from covering receptacle 21. In particular, even though the first receptacle may be protected by a lever actuated cover plate, the receptacle remains vulnerable to the same tampering, vandalism, and misuse problems. The cover plate 62 can be manually operated by anyone having access to the power panel, thus, the problems described above still apply. Gum, debris and other items may be inserted in the receptacle once the cover plate 62 has been moved out of position. Therefore, there is a need in the art to reduce the likelihood of uncovering the receptacles of a power distribution panel employing sequential coupling guards with cover plates.
Another problem associated with such panels is the removal of plugs from receptacles. Uncoupling plugs from receptacles while under load can result in injury to the operator or damage to equipment. As described above in relation to the first unblocked receptacle, power distribution panels are used in many public locations. For instance, the panel might be supplying power to a ride at a carnival where removing power while the ride is in motion would result in leaving guests suspended in midair, upside down or worse. In other situations, power might be removed in the middle of a play or concert at a theater. The same temptation to tamper with the first receptacle applies to the plugs and opening of the last receptacle. If all plugs are inserted in the corresponding receptacles, the sequential coupling guard locks in place only the plugs prior to the last plug, the guard does not lock the last plug in the receptacle. Removal of the last plug subjects both the plug and receptacle to misuse and/or vandalism. In addition, if the last plug is removed, each of the prior plugs locked in place by the subsequent plugs become removable in reverse insertion order and the plugs and corresponding receptacles are subject to tampering and uncoupling. Therefore, there is a need in the art to reduce the likelihood of removal of the last plug of a power distribution panel employing sequential coupling guards.
Accordingly, an object of the present invention is to reduce the likelihood of uncovering the receptacles of power distribution panels.
It is another object of the present invention to reduce the likelihood of removal of plugs from receptacles of power distribution panels.
The present invention is an apparatus for locking a power distribution panel. The power distribution panel has one or more receptacles for receiving one or more plugs with one or more of the plugs and corresponding receptacles being vulnerable to misuse and removal. To reduce the likelihood of misuse prior to plug insertion, a locking cover plate is mounted in the power distribution panel for controlling access to a receptacle. To reduce the likelihood of misuse and/or removal subsequent to plug insertion, a locking device is associated with the power distribution panel for locking in place a plug in a receptacle.
Another aspect of the invention relates to a method of locking a power distribution panel. The power distribution panel has one or more receptacles for receiving one or more plugs with one or more of the plugs and corresponding receptacles being vulnerable to misuse and removal. A locking cover plate is mounted in the power distribution panel for controlling access to a receptacle. A locking device is associated with the power distribution panel for locking in place a plug in a receptacle. The method comprises the steps of unlocking the locking cover plate covering the receptacle, sequentially inserting and rotating plugs in receptacles causing opening of subsequent receptacle cover plates, inserting the last plug in the last receptacle, and locking the locking device retaining the last plug in the last receptacle.
Still other objects and advantages of the present invention will become readily apparent to those skilled in the art from the following detailed description, wherein the preferred embodiments of the invention are shown and described, simply by way of illustration of the best mode contemplated of carrying out the invention. As will be realized, the invention is capable of other and different embodiments, and its several details are capable of modifications in various obvious respects, all without departing from the invention. Accordingly, the drawings and description thereof are to be regarded as illustrative in nature, and not as restrictive.